Always replace ur radiator cap 1st, before doing doing any diagnostics on cooling system. it costs only Rs90/-. but its the cauz of 80% heating problems & can even lead to engine seizure.
Then pour in some coolant in ur system. this will not only prevent overheatin/ rust but also helps in indicating minor water leaks. whenever coolant leaks from anywhere it leaves colored marks at that place after evaporating.
leaking water might not drip but evaporate instantly due to engine heat so do as told above.
Engine over heating is also caused by over advanced ignition timing. so check timing with a timing light/gun. our mechanics dont hav timing light & set timing by experience.
Check ur thermostat valve for proper functioning. Always replace it if faulty.
If everything else fails change ur water pump. we do everything like changing radiator, servicing, water hoses but we dont check water pump. bhai its a mechanical thing & always immersed in water. if water can corrode the head then it also corrodes the water pump.
also try using radiator flush available in market. it will help unblocking the internals in the engine.
Finally
Always fill in with coolant/ water with ur heater at ON position & keep the engine running with radiator cap removed for about 5 mins. it will help in removing air bubbles from cooling system.
I once had overheating problem & luckily b4 doing anything i found out that my overflow pipe which connects from radiator to reserve bottle was blocked. check this pipe for blockage periodically.
